Fair - you could host a copy or a link (or a sort of combination between the two, I guess), but it wouldn't transfer the ownership of the original post. I'm still not sure this is such a pressing feature that I accept it as the actual raison d'etre of AT proto, especially considering how it very much exists there only in theory at best. But it is interesting technology, and something they could maybe have worked with ActivityPub to try to achieve.
I'm glad to hear that maybe Bluesky is more decentralized than I suspect, but Bluesky engineer whose blog post you linked still links to his bluesky account on bsky.social. If running a separate instance is achievable, I would love to see people actually do it.